Know-How: OPC UA Client Server Communication Explained (Simple Guide)

Introduction

Modern industrial systems require machines, software and cloud applications to communicate seamlessly. However, different vendors often use different communication protocols making integration complex.

OPC UA (Open Platform Communications Unified Architecture) solves this challenge by providing a standard, secure and reliable communication framework that enables machines and software systems to exchange data efficiently.

Among the available communication models, Client Server is the most commonly used approach in industrial automation systems.

This article explains OPC UA Client Server communication in a simple and practical way.

What is OPC UA Client Server Communication?

OPC UA Client Server communication works like a question answer system between software applications and industrial devices.

• The OPC UA Server acts as the data provider

• The OPC UA Client acts as the data consumer

• The client requests information

• The server responds with structured data

This communication model follows a request response mechanism, ensuring reliable and structured data exchange between systems.

Simple Analogy

Imagine a classroom:

• Teacher has knowledge → OPC UA Server

• Student asks questions → OPC UA Client

• Teacher provides answers → Data response

  
  

Similarly:

• A machine stores temperature or speed values → Server

• A monitoring system requests those values → Client

• The server responds with real time data

  
  

Example:

Client asks:

What is the motor speed?

Server responds:

Motor speed is 1450 RPM

How OPC UA Client Server Works

The communication process typically follows these steps:

1. A machine, PLC or device exposes data through an OPC UA Server

2. A SCADA system, dashboard or application connects as an OPC UA Client

3. The client requests data points such as temperature, pressure or energy consumption

4. The server securely returns the requested information

   
   

Because OPC UA is platform independent, clients and servers from different vendors can communicate without compatibility issues.

Where is OPC UA Client Server Used?

OPC UA Client Server communication is widely used across Industry 4.0 and Industrial IoT applications:

• Factory automation systems

• PLC to SCADA communication

• Energy monitoring solutions

• Machine condition monitoring

• Industrial IoT platforms

• Edge to cloud integration

  
  

Its vendor neutral architecture allows seamless integration between legacy equipment and modern digital systems.

Key Benefits

OPC UA Client Server communication provides several advantages:

• Secure communication using encryption and certificates

• Reliable and structured data exchange

• Interoperability between multi-vendor devices

• Scalable architecture for small to large systems

• Supports real time monitoring and analytics

OPC UA Information Model in Client Server

One of the most powerful features of OPC UA is the Information Model, which defines how data is structured and described inside the server. Instead of sending raw values, OPC UA organizes data in a meaningful and standardized format. Think of it like a digital library where information is arranged logically.

Basic Elements of the Information Model

OPC UA structures data using:

• Objects : Represent real-world entities such as machines, sensors, or production lines.

• Variables : Represent values such as temperature, speed, pressure, or energy consumption.

• Methods : Represent executable actions such as start, stop, reset, or calibrate.

• Properties : Provide additional details describing objects or variables.

Example Information Model Structure

Factory

└── Machine 1  

├── Temperature = 65°C  

├── Speed = 1450 RPM  

└── Status = Running

Because the data is organized hierarchically, the client can easily browse and understand the structure of the machine information.

This structured approach improves interoperability between different systems and simplifies integration efforts.

Why Information Modeling Matters

Without a structured information model:

• Data meaning may be unclear

• Integration becomes complex

• Interoperability becomes difficult

With OPC UA Information Modeling:

• Data has clear meaning

• Systems understand context

• Integration becomes faster

• Reusability improves

One Line Summary

OPC UA Client Server communication enables machines and software applications to exchange data securely using a structured and standardized question answer approach.